Assay conditions can influence the outcome of cytotoxicity tests of nanomaterials: Better assay characterization is needed to compare studies

BackgroundReliable in vitro studies that generate consistent toxicity data on nanomaterials on a high-throughput scale will be of invaluable significance in the next few years.AimIn this study, we checked the influence of several steps of the experimental design on the outcome: we investigated the role of cell density, viability assay and particle dispersion method, including the influence of serum and effect of a surfactant (Tween 80).MethodsThe dose–response curve was assessed for ground multiwalled carbon nanotubes (CNT) and the silica benchmark Min-U-Sil, on lung epithelial cells (A549 cells) and macrophages (stimulated THP-1 cells).ResultsThe cell density used in the cytotoxicity study has an impact on the outcome: for the same concentration of Min-U-Sil, the viability of A549 cells varied from 10% to 55% with increasing cell density. Whereas foetal calf serum attenuated the cytotoxicity of Min-U-Sil, this effect was not seen for CNT. The results show how cell culture conditions can modify the outcome of a toxicological experiment, as shown in this study for Tween 80 to disperse the test agent.ConclusionsThese experiments illustrates that results reported in literature can only be compared when, in addition to the use of a benchmark particle, a detailed method description is available. Therefore, more emphasis is needed on a standardized design for cytotoxicity studies.